850, S70, V70, C70 Engine does not start, failed start
 

Hello people. For about 3 years I have had a problem with my C70 (1998) not starting the engine. Starter motor turns, but the car does not start. Sometimes for several months the problem does not appear, while in some periods it almost always does (both in winter and in summer). Then when I manage to start it, the car is perfect. I recently replaced (original Volvo purchases): air mass meter (I had very high consumption and irregular engine) and accelerator position sensor (gear changes were out of order and the car jerked), both problems solved. While years ago I bought new ones: distributor cap, distributor rotor (Facet brand), spark plug cables (Tesla Made in Czech brand) and spark plugs (original Volvo for C70 Turbo). While they are still original, never replaced: starter motor and coil. My 1998 C70 is very similar to the Volvo 850 95/96/97, as it still has only 1 ignition coil, cable throttle, no phase shifter. What can I check to fix the problem? I want to underline that if I manage to get it started, the car is perfect with the engine.

I could be very well wide of the mark here but my first thought on reading the post was the antenna ring which sits around the ignition barrel.When my V70 used to act like yours seems to be i.e. engine spins over but no start but when it does start runs perfectly that was my problem.Fortunately I cured mine by cleaning the contacts in the wiring plug.

I had had problems with the immobilizer antenna around 2014. The car no longer started, but the starter motor turned continuously with a lot of force. Bought a new original Volvo immobilizer intenna and solved the problem. Now, however, if it does not start, the starter motor does not make a very convincing noise. Maybe I could have the electrician replace the starter motor brushes?

Today a missfire

When accour this problem i try to accelerate. I not know if after a lot of tentative start thanks of acceleration or not.

I post video (excuse me of excess of soap near hour and reset knob, i fix this problem in future):

https://youtu.be/hJuyxNn2ERE

Before dropping the starter motor off to check the brushes I'd check the earth connection from the battery to body is clean and tight[I assume the battery is in good shape?]also check the engine to body earth strap is in good condition and the connections are clean and tight.then check that all connections to the starter are clean and tight too-especially the small trigger wire.I don't know if the misfire is a related issue or not.

Battery is amazing: Optima AGM 1000A as new.
Cable? To + and - of battery i was pleaced grease.
I'll check other cable.

What type of grease have you used on the cable? It is not a good idea to use ordinary multi-purpose grease on electrical components. Use battery terminal grease or something similar specifically designed for keeping corrosion away on electrical terminals / joints.

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I asked for specific battery grease from both Volvo, Mercedes-Benz, auto parts near home that sold me the batteries of my cars. They just gave me generic grease, like CV joints. This morning with the engine cold, I had my wife start the engine 3 times. I made a video. No problem today. Yesterday, however, he did not want to leave.

https://youtube.com/shorts/fbGaUnugDEA?feature=share